Recognition of Dual or Multiple Pathology in Skin Biopsies from Patients with HIV/AIDS

A large percentage of patients with HIV/AIDS will develop dermatological complications. Consequently, all practising clinicians and pathologists in regions with a high prevalence of HIV/AIDS must be familiar with the diverse cutaneous manifestations of the disease. This paper highlights the fact that biopsy material in this clinical context may occasionally reveal more than one pathological process. The potential spectrum includes two or more infections in a single skin biopsy (e.g., herpes simplex and cytomegalovirus infection), neoplastic lesions containing infective organisms (Kaposi sarcoma (KS) and cryptococcosis), dermatoses in association with neoplastic lesions (e.g., KS and interface dermatitis), or more than one dermatosis in a given specimen (e.g., papulopruritic eruption and nodular prurigo). Rare biopsies may even demonstrate triple pathology. The importance of careful examination of skin biopsies in this clinical context is emphasised. Failure to recognise an undiagnosed concomitant opportunistic infective pathogen could have potentially disastrous consequences for the patient.


Introduction
Dermatological disorders are common in patients with human immunodeficiency virus (HIV) infection and the acquired immunodeficiency syndrome (AIDS). It is said that more than 90% of HIV+ patients will develop cutaneous complications during the course of their illness, and in a significant proportion of these individuals, skin lesions may be a presenting symptom or sign of previously undiagnosed HIV infection [1,2]. The spectrum of HIV-related skin disease includes a wide range of noninfective dermatoses, infective conditions, adverse drug reactions, and neoplastic proliferations [1]. It is not uncommon for this group of patients to manifest with more than one concurrent integumentary condition. Consequently, any given skin biopsy from an individual with cutaneous lesions in the presence of underlying HIV/AIDS could potentially reveal more than one pathological process. In severely immunosuppressed patients who have not received highly active antiretroviral therapy (HAART), subtle features of a coincidental potentially lethal opportunistic pathogen (e.g., cryptococcosis) can easily be overlooked in a specimen predominated by the primary pathological lesion (e.g., Kaposi sarcoma (KS)) [1,3,4]. Although dual or multiple pathological processes are seldom encountered in single skin biopsies in everyday practise, it is always wise to maintain a high index of suspicion when examining specimens from HIV/AIDS patients.
The main objective of this paper is to draw the surgical pathologist's attention to the potential spectrum of dual or multiple pathology, using personally encountered case examples to illustrate this uncommon phenomenon.    reflection of marked underlying immunosuppression. Some more recently reported examples, however, have been a manifestation of the immune reconstitution inflammatory syndrome (IRIS) [3][4][5]. Although a detailed account of the cutaneous manifestations of IRIS is beyond the remit of this paper, many of the viral, fungal and bacterial infections alluded to below, and even neoplasms such as KS, may be a reflection of IRIS [3]. Satisfactory clinicopathological correlation is thus facilitated by knowledge of the patient's CD4 T-cell count and an indication of whether or not HAART has been implemented. The wide spectrum of potential colesional skin biopsy pathology is outlined in Table 1. This spectrum encompasses dual noninfective dermatoses, dual or multiple infections,

neoplasia (KS) in association with infection, neoplasia (KS)
with an associated dermatosis, mixed infective and inflammatory dermatoses, dual neoplastic conditions, and multiple pathologies. Although this latter group is uncommon, a high index of suspicion should always be maintained [1]. In most cases, the detection of more than one pathological lesion in a single biopsy is fortuitous and unexpected. On other occasions, however, a detailed history might reveal that the patient has clinical evidence of more than one type of skin lesion. Some dermatologists may therefore elect to intentionally sample overlapping lesions in a single biopsy [1].

Dual Noninfective Dermatoses.
Since HIV/AIDS may be associated with a diverse array of noninfective dermatological disorders, and patients may often have more than one skin disease at presentation, it is somewhat surprising that skin biopsy specimens seldom reveal dual pathology of a noninfective nature. Two conditions, however, are known to sometimes demonstrate dual pathology. The first of these is pruritic papular eruption of HIV (papulopruritic eruption), where the longstanding pruritis and excoriation may be complicated by superimposed changes of nodular prurigo [6]. The second condition is papular mucinosis of HIV/AIDS, where intradermal mucin deposition is accompanied by concomitant epidermal changes of an eczematous dermatitis, as illustrated in Figure 1 [6-8].

Dual Infections.
The increased susceptibility to infection by a wide range of opportunistic pathogens is a hallmark of HIV/AIDS. It is, therefore, essential that histological specimens in this clinical context are always examined carefully to ensure that a second (or perhaps even a third) infective organism is not overlooked [1]. The most frequently encountered copathogen is cytomegalovirus (CMV). CMV is often identified in the dermis in biopsies obtained from genital or perineal ulcers caused by herpes simplex virus (Figure 2), and associated vasculitis is not uncommon [1,[9][10][11]. CMV infection has also been documented in association with bacillary angiomatosis (BA) ( Figure 3) and mucormycosis [12,13]. The author has also encountered a case of widespread cutaneous ulceration due to vasculitis in the presence of acanthamoebiasis and concomitant CMV infection (Figure 4). Although skin lesions due to infection with Acanthamoeba spp. may occur in patients with AIDS, to date there have been no additional examples with CMV coinfection recorded in the literature [14][15][16][17]. Cutaneous infection with Pneumocystis jiroveci (formerly P. carinii) is a rare complication of HIV/AIDS. There have, however, been single case reports of coinfection with other organisms, namely, botryomycosis due to concomitant Staphylococcus aureus infection, and skin lesions harboring both Pneumocystis organisms and Cryptococcus neoformans yeasts [18,19]. BA has been reported in association with Mycobacterium avium-intracellulare (MAI) infection [5,20]. Cases with lesions containing three separate infective organisms are discussed in Section 2.8.

Dual Infective and Noninfective
Dermatoses. This phenomenon has, to the best of one's knowledge, not been addressed in the literature. Vacuolar interface dermatitis is a reaction pattern with a number of potential causes in patients with HIV/AIDS. Causes are diverse, including the acute exanthem of HIV infection, a morbilliform drug rash, erythema multiforme, and so-called AIDS interface dermatitis [1]. Doubt has been expressed regarding the validity of the latter as a distinct clinicopathological entity, as a significant proportion of patients whose biopsies revealed interface dermatitis had one or more opportunistic infections and/or had been receiving one or more drugs at the time of diagnosis [1,6,21,22]. There are nevertheless occasions in which interface dermatitis is detected coincidentally in a biopsy performed for another reason (e.g., confirmation of KS) and in which there is no significant drug history (see below) [1,6]. The author has encountered cases where careful clinical correlation has elucidated the cause of this reaction pattern when a skin biopsy has been performed for confirmation of another condition. Anecdotal examples include histoplasmosis with erythema multiforme (Figure 5), and folliculitis in association with an adverse drug reaction to HAART ( Figure 6).

Neoplasia in Association with
Infection. KS skin lesions may rarely contain coincidental infective organisms. Failure to recognise the opportunistic pathogen, whose presence is often masked by the more obvious background spindle cell proliferation, could have grave prognostic implications. To date there have been only nine recorded cases of AIDSassociated KS with colesional cryptococcosis, one of whom had oral lesions exclusively [4,[23][24][25][26][27]. The author has encountered three additional examples of KS with incidental Cryptococcus neoformans infection, including the case illustrated in Figure 7.
Histoplasma capsulatum coexistent with KS in a single lesion has also been reported [28]. In this context, H. capsulatum yeasts should be distinguished from infection with capsule deficient forms of C. neoformans occurring in association with KS [3,4]. There are two documented cases of KS with apparent intralesional Candida organisms. The latter were identified on ultrastructural examination [29]. Although there are rare reports of patients with concurrent KS and BA, these cases seem to have presented with separate lesions, showing no apparent microscopic evidence of BA in the KS histological specimens and vice versa [30][31][32].
MAI infection has uncommonly been documented in association with KS, including one patient who had a facial non-Hodgkin lymphoma of immunoblastic type containing acid-fast organisms, and another who had concomitant colesional cryptococcosis [26,[33][34][35]. More recently, M. tuberculosis has also been detected in KS cutaneous lesional tissue (Figure 8), where its presence may serve as a clue to underlying HIV infection, systemic tuberculosis, noncompliance to antituberculous medication, or multidrug resistant tuberculosis [36]. Although these tuberculoid granulomas are recognised with relative ease in involved KS lesions, mycobacterial spindle cell tumours concomitant with KS may pose a particular diagnostic challenge [3]. This latter phenomenon has been described in the lymph nodes of HIV+ patients but has not, to the best of one's knowledge, been documented in the skin [37].
Not unexpectedly, KS may occasionally harbour CMV inclusions, including KS involving the oral cavity [3,38,39]. Although the clinical significance thereof is the subject of debate, the identification of CMV inclusions in KS may serve as a sentinel for more serious systemic CMV disease such as retinitis or pneumonitis [3,38]. The fortuitous detection of molluscum contagiosum in KS has also been reported; the presence of both lesions in a single histological specimen may be the first clue to underlying HIV infection/AIDS [3,40].

Neoplasia in Association with Noninfective Dermatoses.
Since patients with HIV/AIDS often present with cutaneous lesions caused by more than one disease, it is not entirely unexpected that biopsies performed for histological confirmation of KS may sometimes show evidence of a concomitant noninfective dermatosis. Although uncommon, it has been the author's experience that incidental interface dermatitis is encountered occasionally in the epidermis overlying a KS lesion [6,41]. While some examples are almost certainly attributable to a concurrent adverse drug reaction, some cases have no significant pharmacological history and could perhaps represent examples of so-called "AIDS interface dermatitis" [1,6,21,22]. There is a well-documented association between AIDS and acquired ichthyosis, including patients who have presented with concomitant KS [42][43][44]. Biopsies from such patients may therefore reveal histological features of both conditions, as depicted in Figure 9 [41]. The latter biopsy was intentionally obtained from an area of ichthyosis overlying a suspected dermal KS lesion on the lower extremity.

Dual Neoplastic
Lesions. AIDS carries an increased risk of oral and anogenital neoplasia [6,45,46]. Rarely, biopsies of KS genital lesions may reveal coincidental squamous cell carcinoma in situ, as illustrated in Figure 10 Figure 11) [1]. The patient whose biopsy is depicted in Figure 11 had purple-red KS lesions and an associated vesicular eruption. The sample was intentionally obtained from a somewhat haemorrhagic lesion on the trunk, where a vesicle was observed on the surface of a clinical KS lesion.

Conclusion
Colesional pathology may easily be overlooked in skin biopsies from patients with HIV/AIDS, especially when the primary pathological lesion dominates the histological picture. It is wise for the surgical pathologist to always consider dual or multiple pathology when examining biopsy material from this group of patients. Rigorous adherence to this principle when studying the routine haematoxylin and eosin (H&E) stained sections will usually facilitate diagnosis or at least raise suspicion for a second or perhaps even a third pathological process. Since it is neither practical nor cost-effective to perform a panel of histochemical and/or immunohistochemical stains for potential identification of infectious organisms on each and every biopsy, relevant stains should be reserved for confirmation of one's suspicion based on the H&E findings. If necessary, additional biopsies should be recommended for appropriate microbiological studies, such as fungal culture. A clinical history of polymorphous skin lesions should alert the pathologist to the potential for dual or multiple pathology in a given skin biopsy. CMV remains the most frequently encountered coincidental pathogen, and whilst its precise pathological significance is often uncertain, one should remain cognisant that the presence of CMV inclusions in a skin biopsy may serve as a sentinel for more serious systemic involvement [3]. The detection of tuberculous granulomas or Cryptococcus organisms in KS has similar implications [3,4,36]. Although the patients whose biopsies are illustrated herein were largely HAART-naïve, awareness that colesional pathology may be a rare manifestation of IRIS is appropriate in the era of HAART. A potentially interesting collaborative research opportunity may reside in a detailed clinicopathological analysis of a series of such cases.