Phaeohyphomycosis of the Face Masquerading as Basal Cell Carcinoma in an Immunocompetent Patient.

Pheohyphomycosis is a rare heterogeneous group of mycotic infections caused by dermatiaceous (phaeoid) fungi affecting the skin, subcutaneous tissue, and the central nervous system.Involvement of the face is extremely rare, and very few cases have been reported in India so far. We reporta case of phaeohyphomycosisin a 45-year-old female with 1-year history of a well- defined hypertrophic plaque over the right cheek advancing towards the forehead. The lesion was ulcerated with rolled-up margins; a provisional clinical diagnosis of basal cell carcinoma was given. Histopathology of the skin biopsy revealed numerous multinucleated giant cells and fungal hyphae with in and in between the giant cells. Various histochemical stains were used toconfirm the presence of fungal hyphae. Melanin pigment in the fungus was demonstrated with Masson's Fontana stain. Based on the histopathological and histochemical findings, a diagnosis of phaeohyphomycosis was given and it was concluded that the disease was more of a histopathological than clinical diagnosis. This case is being reported due to its unusual presentation and it also highlights the importance of histopathology in the diagnosis of this rare disease.

Introduction

Phaeohyphomycosis, meaning dark fungus with hyphae, is a rare infection caused by dematiaceous/melanizedfungi that aredistributed worldwide. They can involve the skin, subcutis, paranasal sinuses, or the central nervous system.[1] In the skin, these hyphae appear brown-walled due to their ability to deposit melanin pigment.[2] Multiple cases of subcutaneous phaeohyphomycosis involving the leg, foot, toes, arm, left thumb, hand, nails, wrist, waist, or the buttock have been reported from India.[3] Involvement of the face is extremely rare, and very few cases have been reported in India so far.[1]

Case Report

A 45-year-old female from Nepal presented in the Dermatology outpatient department with 1-year history of a well-defined hypertrophic plaque over the right cheek advancing towards the forehead. The lesion showed ulceration and crusting with rolled-up margins. It was associated with itching and erythema along with atrophy and telangiectasia. She had no medical illnesses or any surgicalprocedures in the past. The provisional clinical diagnosis ofbasal cell carcinoma (BCC) was considered, and a punch biopsy skin specimen from the forehead was taken for histopathology.

Hematoxylinandeosin-stained sections revealed epidermal hyperplasia and a diffuse, dense lymphohistiocytic infiltrate along with numerous foreign body and Langhans giant cells in the dermis. Branching, septate, brown-colored fungal hyphae were observed both within and in between the giant cells [Figure 1a and b].

Figure 1

(a) Photomicrograph shows a dense lymphohistiocytic infiltrate along with numerous giant cells in the dermis. Brown colored fungal hyphae are seen both within and in between the giant cells (arrows). (Hematoxylin and eosin 10×). (b) High power view of the same showing brown colored septate fungal hyphae within the giant cells. (Hematoxylin and eosin 100×)

Histochemical staining for periodic acid Schiff (PAS), Masson's-Fontana (MF) and Grocott's Methanamine silver (GMS) stains was performed. PAS stain revealed bright magenta-colored hyphae [Figure 2a], where as silver stain revealed brownish black hyphae with branching septae [Figure 2b]. MF demonstrated melanin pigment in the fungus [Figure 2c].

Figure 2

(a) Periodic acid Schiff (PAS) staining showing bright magenta colored fungal hyphae with branching and prominent septations. (PAS 40×). (b) Grocott'sMethanamine silver (GMS) showing black-colored, septate, and irregularly branching fungal hyphae in the dermis. (GMS 40×). (c) Masson's-Fontana (MF) showing brown-to-black colored fungal hyphae in the dermis. (MF 100×)

On histopathology, the final diagnosis of phaeohyphomycosis was made. Species identification could not be done as after the biopsy the patient did not return for the collection of her histopathological report and the specimen for culture could not be obtained.

This case is being reported due to its unusual presentation and it also highlights the importance of skin biopsy and histochemical stains in the diagnosis of this rare disease.

Discussion

Phaeohyphomycosis iscaused by group of dermatiaceous fungi (brown moulds), which grow in tissues in the form of dark-walled septate mycelium. This mycelial tissue morphology separates phaeohyphomycosisfrom other types of brown-pigmented fungi where the tissue morphology of the organism is either a grain, as in mycoticmycetoma, or a sclerotic body, as in chromoblastomycosis.[4] These opportunistic fungi mostly infect immuno compromised patients and may remain localized or spread via lymphatics.[15]

Clinically, they present as superficial, cutaneous, subcutaneous, or systemic (disseminated) forms.[6] Phaeohyphomycosismay range from a localized superficial infection of the stratum corneum, known as tinea nigra, to subcutaneous cysts known as phaeomycotic cyst to invasion of the brain.[4] Subcutaneous phaeohyphomycosis is the most common sub-type and occurs due to wound contamination or traumatic inoculation of the saprophytic fungus from soil, decaying wood, and vegetation.[7]

In our case, the lesion clinically mimicked BCC because it was ulcerated with rolled-up margins. A differential of lupus vulgaris was also considered keeping in view an ulcerated plaque-like presentation. Because on histopathological examination a definitive diagnosis of phaeohyphomycosis was made by the demonstration of dematiaceous fungal elements in tissue, we can say that the disease is more of a histopathological than a clinical diagnosis. Phaeohyphomycosis is often seen in an immunocompromised state or preceded by a history of injury, however, both these predisposing factors were absent in our case.

The various agents causing phaeohyphomycosis are so similar in morphology that they cannot be differentiated solely on histopathology. Culture is the only definitive method of distinguishing various species of these fungi. Because these dematiaceous fungi are well-known airborne contaminants, a positive culture from a nonsterile specimen should be supported by direct microscopy to be considered significant.[4] Hence, interpretation should be done in conjunction with the clinical presentation, culture report, direct microscopy, and histopathology.[2] Various dematiaceous hyphomycetes have been identified as the etiological agents, especially species ofExophiala, Phialophora, Wangiella, Aureobasidium, Cladosporium, Curvularia, andAlternaria.[4] Of these, the most common is Exophialajeanselmei.[5]

In our case, culture could not be performed for the specific identification of the etiological agent as the patient was lost to follow-up. Identifying the specific agent is very importantbecausedifferent species may have tropism for different organs with varying response to antifungals. Gene sequencing of the internal transcribed spacer region is the most widely accepted molecular method becauseit can discriminate between inter and intraspecies variations.[8]

Surgical excision is the chief modality of treatment with or without antifungal therapy. There are no standardized treatment protocols, however, itraconazole at a dose of 200 mg twice daily helpsindividuals who areunwilling to undergo extensive debulking surgery.[9] While oral itraconazole is considered the empiric drug, voriconazole andposaconazole also show consistent in vitro activity against this group of fungi.[8]

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Conflicts of interest

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