Case report: clear cell hidradenocarcinoma of the nail bed

Dear Editors,

Clear cell hidradenocarcinoma is a rare tumour of eccrine sweat gland origin that occurs conventionally for the head and neck 1. It has indolent growth pattern and higher incidence of regional and distant metastases. No established treatment method has been reported so far due to its rarity and scarce reports. In previous studies, surgical excision, lymph node dissection, chemotherapy, or radiation therapy was suggested as a treatment method. We would like to report a case of a clear cell carcinoma occurring on the nail bed as primary site.

A 76‐year‐old woman presented with thickened nail bed of the left index finger with a darkish discoloration that was gradually increasing in size. The nail had thickened and its contour showed a convex shape with mild tenderness (Figure 1). Although not confirmed objectively, she complained that she had a small amount of transparent discharge from her finger tips. Judging from her age and medical history of diabetes, our initial impression was a chronic fungal infection. So we prescribed topical antifungal ointment and took a biopsy of the mass margin. The pathological result was chronic active inflammation with no fungal hyphae. The presented case was misdiagnosed as chronic active inflammation with severe plasma cell infiltration in the biopsies because of inadequate volume of the specimen – epidermis and superficial dermis only. For second histopathological diagnosis, a partial biopsy of the mass was done under local anaesthesia. The tumour size was 15 × 8 × 2 mm³ and invasion depth was 2 mm. Microscopically, the lesion showed a poorly circumscribed intradermal nodule with infiltrative growth (Figure 2). The tumour cells were exhibited small lobules, nests and cords and partly cystic portion. The tumour cells had morphology similar to that of nodular hidradenoma. The tumour was composed of highly atypical cells with nuclear hyperchromatism, prominent nucleoli and abundant clear cytoplasm. Mitoses were sparse. Neither vascular nor perineural invasion was found. Immunohistochemically, the tumour cells were nuclear strong positive for p63 (Figure 3A) and focal positive for cytokeratin (Figure 3B). The Ki‐67 proliferating index was 3%. In addition, the tumour was negative for epithelial markers [EMA, CK7, CK8/18(CAM 5.2), CK19], melanocytic markers (HMB45, Tyrosinase, Melan A, S‐100), clear cell renal cell carcinoma markers (vimentin, RCC, PAX8, CD10) and Smooth Muscle actin (SMA). The final pathologic analysis confirmed the diagnosis of clear cell hidradenocarcinoma. Upon physical and radiological examination, there was no evidence of distant metastasis or lymph node metastasis, so no chemotherapy or radiotherapy was performed. One month after secondary surgery, we planned the surgery for complete excision of the tumour under local anaesthesia. In order to avoid amputation, the cancer margin was confirmed upon doing a frozen biopsy of a nail bed slice shaving. There has been no local recurrence or distant metastasis during 1‐year follow‐up (Figure 4).

Figure 1.

A 76‐year‐old woman presented with thickened nail bed of the left index finger with a darkish discoloration that was gradually increasing in size.

Figure 2.

Histological features of the clear cell hidradenocarcinoma [hematoxylin and eosin (H&E) staining]. (A) Microscopically, the lesion shows a poorly circumscribed intradermal nodule with infiltrative growth (×1·25). (B) The tumour is composed of small lobules, nests and cords and a partly cystic portion (arrow; ×10). (C) The tumour shows rare small ductal structures (arrow) and intracytoplasmic vacuoles. The tumour cells have morphology similar to that of nodular hidradenoma (×20). (D) Highly atypical tumour cells with nuclear hyperchromatism, prominent nucleoli and abundant clear cytoplasm (×40).

Figure 3.

Immunohistochemical findings of a clear cell hidradenocarcinoma. (A) Nuclear strong positivity for p63 (×10) and (B) focal positivity for cytokeratin (×10).

Figure 4.

Six‐months after wound healing. There has been no local recurrence or distant metastasis during 1‐year follow‐up.

Clear cell hidradenocarcinoma is an extremely rare eccrine neoplasm, which has been documented in less than 70 cases in the literature 1, 2. After 20 years of the first report of clear cell hidradenoma by Liu in 1940s, several histochemical studies have found that these tumours arise from eccrine sweat glands 3. These tumours are aggressive, with an approximate 50–75% rate of recurrence and the possibility of metastasis and it often develops in head and neck lesions 2, 4. Immunohistochemistry can be utilised to make differential diagnosis of these tumours. Hidradenocarcinoma is positive for cytokeratin, CEA and EMA, may shows positivity for p63, vimentin, GCDFP‐I5 and estrogen receptor, and is negative for S‐100 protein 5. Surgery is the first‐line treatment, consisting of wide excision ensuring negative margin. Other strategies include block dissection of involved nodes followed by radiotherapy and chemotherapy if there is distant metastasis 5.

This is the first case report of hidradenocarcinoma with nail bed as the primary site. When she first visited our clinic, we misdiagnosed it as nail dystrophy due to typical chronic fungal infection. Because, the patient was of old age and poor health state there was no other remarkable symptoms. Only a small amount of transparent discharge was notable. We did not suspect cancer initially, but we eventually detected cancer based on the findings of non‐typical patterns, and could provide the patient with appropriate treatments. To conclude, as stated above, when healing of the nail is delayed due to chronic inflammation, malignancy should be suspected. A histopathological study must be conducted to rule out tumour and infection.

Eun T Son1, Hwan J Choi1 & Hyun J Lee2
1Department of Plastic and Reconstructive Surgery, College of Medicine, Soonchunhyang University, Cheonan, Korea
2Department of Pathology, College of Medicine, Soonchunhyang University, Cheonan, Korea
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