A 55-year-old male truck driver with hypertension and type 2
diabetes had a history remarkable for a mass of the right groin,
treated with surgical excision. Fourteen months after resection of
the mass, the patient was seen in the urgent care clinic for cough.
Chest radiographs were normal and he was treated for bronchitis and
released. Returning 1 month later, he observed that a "knot" had
developed on his head after a blow to the parietal area. Physical
examination showed an approximately 2-cm firm discoid nodule of the
right occipitoparietal area. The "knot" was thought to be a
calcified hematoma and the patient was told to seek follow-up care
if the nodule changed. Four months later, he returned with
complaint of a dry cough and variable headaches and incidentially
requested an examination of the "knot" again. The scalp lesion had
grown and was now boggy to palpation. All laboratory data was
normal.
Diagnosis
Merkel cell carcinoma (MCC)
Discussion
Merkel cell carcinoma, also called cutaneous small cell
undifferentiated carcinoma, is an exceedingly rare entity of
unknown incidence. Arising from neuroendocrine (or Merkel cells) in
the dermis, MCC is thought to share neural crest origins with
malignant melanoma, pheochromocytoma, and neuroblastoma. MCC is
relentlessly progressive, with lymphatic and, less commonly,
hematogeneous spread. Mean time to recurrence is reported to be 8
to 10 months and the 3-year survival rate is 55% to
58%.
1-3 Only nine cases of brain metastases have been
reported to date. This case presentation graphically illustrates
the intensely aggressive nature of this malignancy.
Clinically, MCC may present as a "solitary violaceous dome
shaped nodule or indurated plaque."3 On microscopy,
immunohistologic examination demonstrates epithelial (cytokeratins,
epithelial membrane antigen) and neuroendocrine (neuron-specific
enolase, chromogranin A) markers, confirming
diagnosis.2
While radiography is not diagnostic for MCC, CT imaging of
primary lesions reveals solitary or multiple minimally enhancing
soft-tissue nodules, which may be associated with lytic bony
erosion.4 Lesions are hyper- or isodense in relation to
muscle.5 Metastatic lesions demonstrate target-shaped
lesions with or without ring enhancement;4 and
subcutaneous linear stranding.5 MCC lesions are
hypoechoic on sonography. CT has proven useful in staging
disease,5 as has lymphatic mapping of sentinel nodes by
scintigraphy.
Truncal location,1 size >2 cm, male sex, positive
surgical margins, positive nodes,1,2 and second primary
tumor2 are associated with the least favorable
prognosis. Wide surgical excision and lymphadenectomy with local
radiation is the treatment of choice1-3 with adjuvant
chemotherapy in selected cases.1-3 Octreotide and
natural human tumor necrosis factor have shown promise in limited
trials.6-8
Interestingly, the literature documents a disproportionate
number of spontaneous remissions occurring in this otherwise
devastating disease; the usual incidence of spontaneously remitting
carcinoma is less than 1 in 60,000 to 100,000 cases. Two sources
suggest that regression of the lesions may be associated with dense
lymphocytic infiltrates and apoptosis of peripheral cells in tumor
nests.9,10
ACKNOWLEDGMENT
The authors wish to thank Dr. A. Singh, Laboratory Chief; Dr. P.
Katikaneni, Department of Pathology; and John Baroody, Medical
Photographer; at the Ralph H. Johnson VA Medical Center for their
assistance in preparing this report.
- Ott JM, Tanabe KK, Gadd MA, et al:
Multimodality management of Merkel cell carcinoma. Arch Surg
134:388-392; discussion 392-392, 1999.
- Fenig E, Brenner B, Katz A, et al: The role of
radiation therapy and chemotherapy in the treatment of Merkel cell
carcinoma. Cancer 80:881-885, 1997.
- Verola A, Champeau F: Merkel cell carcinoma
[in French]. Ann Chir Plast Esthet 43:439-444, 1998.
- 4. Eftekhari F, Wallace S, Silva EG, Lenzi R:
Merkel cell carcinoma of the skin: Imaging and clinical features in
93 cases. Br J Radiol 69:226-233, 1996.
- Gollub MJ, Gruen DR, Dershaw DD: Merkel cell
carcinoma: CT findings in 12 patients. AJR Am J Roentgenol
167:617-620, 1996.
- DelRio P, Borgia GL, Lampugnani R: Merkel cell
carcinoma: A report of 3 clinical cases. Min Chiurg 54:179-183,
1999.
- Cirullo F, Filippini L, Lima GF, et al: Merkel
cell tumor: Report of case and treatment with octreotide. Min
Chiurg 52:1359-1365, 1997.
- Hata Y, Matsuka K, Ito O, et al: Two cases of
Merkel cell carcinoma cured by intratumor injection of natural
human tumor necrosis factor. Plast Reconst Surg 99:547-553,
1997.
- Takenake H, Kishimoto S, Shibaki R, et al:
Merkel cell carcinoma with partial spontaneous regression: An
immunohistochemical, ultrastructural, and TUNEL labeling study. Am
J Dermatopathol 19:614-618, 1997.
- Kayashima K, Ono T, Johno M, et al:
Spontaneous regression in Merkel cell (neuroendocrine) carcinoma of
skin. Arch Dermatol 127:550-553, 1991.