Two cases of metastases to the scalp bone mimicking epidermoid cyst
Published Web Locationhttps://doi.org/10.5070/D32w9716jj
Letter: Two cases of metastases to the scalp bone mimicking epidermoid cystFukushima Medical University, Fukushima, Japan
Yasunobu Kato, Nobuyuki Kikuchi, Akiko Nishibu, Mikio Ohtsuka, Toshiyuki Yamamoto
Dermatology Online Journal 17 (12): 13
Metastatic skin tumors present with a variety of clinical manifestations. We herein present two cases of metastases to the scalp, invading the skull, which showed epidermoid cyst-like appearances.
Cutaneous metastases usually assume a nodular, indurated, and inflammatory clinical appearance. Other unusual forms include zosteriform, sclerodermoid, and acquired lymphangioma-like appearances. We describe herein two cases in which metastases occurred in the scalp, invading the skull, from high-grade endometrial stromal sarcoma (ESS) and hepatocellular carcinoma (HCC) and presented as epidermoid cyst-like nodules.
Case 1. A 69-year-old female was diagnosed with ESS of the uterus by cytological examination 1 year prior to presentation. Her tumor was surgically removed 4 months after diagnosis. Histopathology revealed dense and diffuse growth of spindle sarcoma cells, giant cells, with prominent nuclear mitoses, which invaded into the muscle. Immunohistological examination revealed that the tumor cells were positive for vimentin, but negative for desmin and cytokeratin. Thereafter, chemotherapy regimens including ifosfamide and cisplatin were started, but during the follow-up periods, she noticed a mass on the scalp. Physical examination showed a dome-shaped soft cystic mass, which rapidly grew to 5 cm by 4 cm one month later (Figure 1). Examination by ultrasonography also suggested a cystic structure. Excisional surgery was attempted with a presumed diagnosis of epidermoid cyst. However, the encapsulated tumor mass was connected to the galea aponeurotica and pericranium. Histological examination revealed a proliferation of malignant mesenchymal cells with scanty cytoplasm and ovoid atypical nuclei (Figure 2a). The mitotic count in these areas was more than 10 mitoses per high-power field (Figure 2b). Both types of tumor cells were strongly immunoreactive for vimentin (Figure 2c), with a similar pattern to primary ESS. Examination by computed tomography (CT) scanning showed a bony defect of the left side of the skull (Figure 3) and multiple metastases to the bone. Radiation and chemotherapy by topotesin were started, but she died two months later.
|Figure 3||Figure 4|
|Figure 3. CT showed a bony defect of the scull (arrow)|
Figure 4. Clinical appearance exhibits cystic features (Case 2).
|Figure 5. Tumors occupy the inner and outer areas of the scalp, invading the skull.|
Case 2. An 80-year-old male visited our department, complaining of a mass of the scalp, which he noticed 3 months before. He was diagnosed with moderately differentiated HCC by serological and cytological examination 2 years prior to presentation; lung metastasis occurred one year after diagnosis. A physical examination showed a dome-shaped soft cystic mass, 6.5 cm by 6 cm (Figure 4). Examination by CT scanning showed tumor shadow and bony defect of the right skull with inner and outer metastases to the bone (Figure 5). Radiation therapy was started.
ESS is one of the rare malignant tumors of the uterus and is classified into low-grade ESS and high-grade ESS . High-grade ESS assumes more aggressive behavior and grows destructively into the myometrium [2, 3]. Moreover, distant metastases are frequently observed, such as in the lung and pelvis . Histologically, high-grade ESS is made of monotonous sheets of malignant cells with scanty cytoplasm and ovoid nuclei, showing higher mitotic activity . Immunohistochemical studies show that the tumor cells are positive for vimentin, but negative for cytokeratins and desmin. Low-grade ESS shows immunoreactivity for both estrogen and progesterone receptors, whereas high-grade ESS is negative for both hormone receptors. To our knowledge, skin metastasis of ESS has not yet been reported.
Subcutaneous dermoid cysts occur mainly on the head, but are usually noted to be present since birth in most cases, which suggest the sequestration of cutaneous tissues along lines of embryonic closure . In Case 1, we first suspected an epidermoid cyst, because it was cystic and soft on palpation and did not present as a firm nodule. On the other hand, we easily diagnosed the bony metastasis in Case 2, because of the prior experience with Case 1. Our cases are unique because the cystic elevation was formed by bone metastases but not by skin metastases. In addition, the metastatic tumor grew rapidly, affecting the skin. That is the reason why our cases presented cystic appearances. It should be noted that metastasis should be taken into consideration when we see scalp nodules in cancer-bearing patients, even if they exhibit soft and cystic appearances.
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