Primary cutaneous adenoid cystic carcinoma: An unusual case
Hospital Virgen de la Salud Toledo, Toledo, Spain
Primary cutaneous adenoid cystic carcinoma (PCACC) is an uncommon adnexal skin tumor. It is usually located on the head or neck of people over 50 years of age, affecting men and women equally. The etiology is unclear; the source used to be considered the eccrine glands, but more recent hypotheses defend this carcinoma as originating in the apocrine glands or modified apocrine glands. The tumor may clinically appear as a normal skin-colored nodule with ill-defined edges and slow growth. Histologically, a proliferation of neoplastic cells appears, which could present in a tubular, cribriform, or solid pattern. Perineural invasion is characteristic for this tumor. For diagnosis of PCACC it is essential to exclude metastasis, especially in the salivary glands. Treatment involves surgical excision. We present a case of primary adenoid cystic carcinoma in a young woman located on the skin of the upper limb, which is an unusual place.
We describe the case of a 33-year-old woman with no medical history of interest to the current clinical pattern. The patient sought medical attention for a lesion located on the upper left arm that had been growing slowly, progressively, and asymptomatically for 2 years.
Physical examination revealed a subcutaneous nodule with slight erythema, 1 cm x 1.5 cm in diameter, smooth-surfaced, and with a firm consistency on the upper left arm (Figure 1). No locoregional adenopathy or visceromegaly was detected.
A biopsy was performed with the H&E stain showing a well-defined deep dermal nodule consisting of nests of basaloid cells with cribriform and tubular patterns and abundant mucin in the cysts and between cells (Figure 2). The immunohistochemical stains proved positive for epithelial membrane antigen (EMA) and pan-cytokeratin AE1/AE3 (Figure 3). Therefore, the diagnosis is compatible with adenoid cystic carcinoma.
In order to rule out metastasis in the lesion, a CT scan was performed of the neck and thorax and an MRI of the maxillomandibular, neck, and paranasal sinus regions. Neither procedure showed any irregularities, thereby supporting a cutaneous origin.
Excision was performed of the tumor with ample margins and a biopsy of the sentinel node was negative. Currently, after twelve months of follow-up, the patient shows no signs of recurrence.
Adenoid cystic carcinoma may appear in any location in which glands are located. The most common locations are the salivary glands, palate, and submaxillary glands. Other more uncommon locations are the skin, external auditory canal, nasopharynx, lacrimal glands, bronchial tubes, uterine cervix, and breast .
The etiology is unclear; the tumor source used to be considered the eccrine glands, but more recent hypotheses suggest this carcinoma as originating in the apocrine glands and modified apocrine glands [3, 4]. The condition occurs as frequently in men as women, predominantly in people over 50 years of age. It may clinically appear as a normal skin-colored nodule, with ill-defined edges and slow growth [1, 5].
For diagnosis of PCACC it is essential to rule out metastasis, especially in the salivary glands, although this is atypical. Histologically, a proliferation of neoplastic cells appears on the skin and subcutaneous cellular tissue. Perinueral invasion is characteristic for this tumor. Tumoral cells are present in nests made of basaloid cells without skin involvement. A tubular, cribriform or solid pattern may manifest. An immunohistochemical study proves positive for epithelial membrane antigen (EMA) and pan-cytokeratin AE1/AE2 and S100. Some authors describe positive results for carcinoembryonic antigen (CEA). The histological differential diagnosis may include adenoid basal-cell carcinoma, mucinous apocrine carcinoma, and cribriform carcinoma .
Treatment for adenoid cystic carcinoma is not standardized, often consisting of excision with tumor-free margins. Lymphadenectomy is performed when there is a clinical or surgical suspicion of nodal involvement . Given that approximately 50 percent of cases exhibit recurrence, some authors recommend Mohs surgery as the treatment of choice . Adjuvant and therapeutic radiotherapy has not been shown to decrease the risk of recurrence. Slow-growing pulmonary metastasis has been described, which responds satisfactorily to surgical and polychemotherapy treatment .
Given an indolent nature and long tumor-free interval prior to recurrences and metastasis, long-term patient follow-up is important .
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