Squamous cell carcinoma of the skin mimicking epidermoid cysts

ARTICLE

Six months before first presenting at our department in June, 1994, an 89-year-old woman had noticed, anterior to her right ear, a nodule that had gradually enlarged without rupture or drainage. During middle age, the patient had worked outdoors for over 20 years. After retirement, a scaly erythema began to appear on her face, and reappeared 7 times in 8 years. All these lesions were removed surgically and diagnosed as solar keratosis. Four out of the seven lesions occurred in front of the right ear. The last excision was performed in March, 1992, from this area. In the patient's family history, both parents and 3 out of 7 brothers and sisters of the patient had died of gastric or lung cancer. A skin-colored, slightly painful nodular lesion 4 cm in diameter suggestive of an epidermal cyst, was observed in front of the right ear (Fig. 1). The local lymph nodes were not palpable. The results of both blood and biochemical examinations were within the accepted limits.

Diagnosis:
squamous cell carcinoma of the skin mimicking epidermoid cysts

Histopathological findings

Throughout the dermis, tumor cells, mainly squamoid cells surrounding horny pearls, were observed, and these tumor cells connected with the epidermis (Fig. 2). A biopsy of the tumor led to the diagnosis of SCC. Ten days after the first operation, a new nodular lesion of similar appearance developed close to the first lesion. This new lesion had a tubular structure composed of tumor cells, and was histologically similar to the first. Electron microscopy revealed that the tumor cells had large nuclei and poorly differentiated tonofibrils, and were attached by poorly developed desmosomes. After the second tumor resection, another lesion appeared in the same area. In view of the patient's age, neither a radical operation nor chemotherapy was performed. The tumor became so large that it occupied the whole right cheek by March 1996 (Fig. 3). We have not been able to find any bronchial, otorhinological, or gynecological tumor, despite repeated examinations using CT scanning and fiberscopy. Tumor markers such as BFP (biological fetoprotein), sialyl Lewis^x-i antigen, NSE (neuron specific enolase), and AFP (alpha fetoprotein) were also negative.

Comments

In the present case, the problem was to identify where the SCC, which formed a skin lesion mimicking an epidermoid cyst, originated. One possibility is that it was derived from an internal malignancy: the breast, stomach and lung are known to be frequent primary sites [1]. However, we could not find any lesions in spite of repeated examinations of these sites. This meant also this skin cancer had not yet metastasized to the internal organs, despite its great size.

The next possibility was that it arose from the solar keratosis that had appeared 7 times previously. We are attracted to this possibility because these tumors arose in a site where solar keratosis had appeared repeatedly. However: (1) some immunological differences have been found between the cells of SCC and those of solar keratosis [2, 3]; and (2) the question remains whether it is possible for solar keratosis to develop into subcutaneous, cystic tumors of SCC accompanied by tumor cells scattered throughout the dermis. Certains factors, such as UVB radiation, are said to induce solar keratosis, which could then develop into SCC. Tsuji et al. [4] pointed out that solar keratosis has been found to have a biological tendency toward malignancy, although the mechanisms that modulate malignancy in solar keratosis remain unknown. It is said that SCC arising from solar keratosis generally does not metastasize [5]. These reports correspond well to our case in which: (1) the patient had been exposed to considerable amounts of sunlight for over two decades in farm works; and (2) no internal malignancies, either primary or secondary, were found.

To remove the solar keratosis, which had appeared repeatedly prior to the new nodular neoplasms, we selected a surgical procedure, since her family history and background suggested that the patient had a relatively high risk of cancer. However, on retrospection, the surgery was not adequate for preventing later formation of SCC. This case suggested that appropriate surgical excision and careful follow-up are required for solar keratosis.

REFERENCES

1. MacKie RM. Senile keratosis. In: Rook A, Wilkinson DS, Ebling FJG, Champion RH, eds. Texbook of Dermatology. 5th ed. Vol. 2. Oxford: Blackwell Scientific Publications, 1992: 1475, 1478-9.

2. Groves RW, Allen MH, Ross EL, et al. Expression of selectin ligands by cutaneous squamous cell carcinoma. Am J Pathol 1993; 143 (4): 1220-5.

3. Ikeuchi T, Urano Y, Fukuhara K, et al. Light-microscopic autoradiographical analysis of [¹²⁵I] epidermal growth factor binding in basal cell epithelioma and squamous cell carcinoma of the skin. J Dermatol 1993; 20 (4): 219-25.

4. Tsuji T, Shrestha P, Yamada K, et al. Proliferating cell nuclear antigen in malignant and pre-malignant lesions of epithelial origin in the oral cavity and the skin: an immunohistochemical study. Pathol Anatom and Histopathol 1992; 420 (5): 377-83.

5. Lever WF, Lever GS. Senile keratosis. In: Histopathology of the skin. 7th ed. Philadelphia: J.B. Lippincott, 1990: 542-6.