A 32 years old woman presented with a subcutaneous nodule of the scalp with associated alopecia (). Three years prior to the presentation she noted an indolent, slowly expanding firm nodular lesion clinically resembling a cutaneous cylindroma or trichoblastoma. In her medical history there was no evidence of previous skin lesions or systemic tumour diseases. At physical examination no signs of systemic disease were found and superficial lymph nodes were not palpable. Haematological tests were also in the normal range. The lesion was surgically excised and submitted for histological examination.
The clinical picture of the scalp lesion with associated alopecia.
Macroscopically the lesion was a 1.9×1.7×2.3 cm grey-tan, flesh tumour, with poorly circumscribed borders. Microscopically it showed a characteristic basophilic appearance on low power magnification due to the nuclear hyperchromatism. The tumour was poorly circumscribed and consisted of medium-small basaloid cells, with scanty cytoplasm and small and inconspicuous nucleoli, arranged in islands, cords and strands with glandular, cystic, cribriform architecture, embedded in a fibrous stroma ( A and B). The lesion invaded the mid and deep dermis but not the subcutaneous fat. The basaloid cells were never displaced in a palisades fashion and no connection to the overlying epidermis was observed. Mitotic activity was very low (1 mitosis ×10 high power field), whereas necrosis, perineural invasion, lymphatic and/or blood vessels infiltration were not present.
Figure 2 Histological and immunohistochemical features of a primary cutaneous adenoid cystic carcinoma A) Low power view of the tumour demonstrating a poorly circumscribed neoplasm, which is composed of collection of basophilic cells with cribriform pattern. B) (more ...)
At immunohistochemistry, as expected, the tumour expressed low and high molecular weight keratins. A variably expression of S-100 protein and carcino-embryonic antigen (CEA) was also observed. The latter was restricted to the luminal spaces (data not shown). To better analyze the tumour at phenotypic level, selected monoclonal antibodies to type IV collagen and epithelial membrane antigen (EMA) were also considered. The former highlighted the hyaline deposits among the basaloid cells and the latter the apical aspects of pseudoglandular areas (). The basophilic intraglandular material, variably detected in the tumour, was also highlighted with alcian blue staining at pH 2.5 and showed immunoreactivity for laminin (data not shown).
Both histological and immuno-phenotypical evaluation suggested the diagnosis of adenoid cystic carcinoma (ACC), but considering the rarity of this entity as a primary skin tumour it was necessary to rule out the possibility of a skin metastasis arising from other malignancies with histological features of ACC.
Adenoid cystic carcinoma, in fact, is most commonly seen as a neoplasm of the salivary glands and seromucinous glands of the upper respiratory tract. It has also been reported to occur in the breast, lung, uterine cervix, prostate, and lacrimal gland.1,8
As a consequence a careful breast and an otolaryngology examination was performed at specialist level, followed by head and neck ultrasonographic scan. A PET-CT scan was also considered to complete the oncological screening. Fortunately, the clinical examination was negative and all the radiological exams resulted in the normal range. All together, the clinical, morphological and immuno-phenotypical features described above, supported the final diagnosis of a primary cutaneous adenoid cystic carcinoma (PCACC). To avoid local recurrences a wide surgical excision with 2 cm disease-free margins was finally performed. After 12 months of follow up the patient is fully recovered without any evidence of disease.