Malignant melanoma of the ovary is very rare and usually
metastatic. Primary ovarian malignant melanoma is even
more rare and most primary cases are thought to develop
on a background of cystic teratoma3,4
presence of widespread melanosis areas in a “mature cystic
teratoma” that we have found in the ovarian cyst resection
material from a 25-year-old patient seems to support this
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|Table I: Definite and probably primary ovarian melanoma cases in the literature
The differential diagnosis includes metastatic malignant
melanoma and primary and secondary tumors of the
ovary. It is also possible for a malignant melanoma that has
regressed to have metastasized to the ovary. The metastases
of the regressed tumor in various organs may be the first
clinical sign in such cases.
The absence of history of malignant melanoma, pigmented
skin lesions or excision, the inability to find another
malignant melanoma focus despite systemic investigation
and the unilateral tumor led us to diagnose this case as
“probably primary malignant melanoma”.
Histology is important for ovarian malignant melanoma
cases but most reports do not contain detailed histological descriptions. The most common type is the epitheliod cell
type with a diffuse or nodular pattern2. The nodular or
“nested” pattern is seen frequently in metastatic ovarian
malignant melanoma5. Metastatic cases are usually
bilateral and can rarely be unilateral.
The differential diagnosis of primary ovarian malignant
melanoma contains a vast variety of pathologies. Metastatic
ovarian malignant melanoma should be differentiated from
malignant lymphoma, indifferentiated carcinoma, PNET
and malignant sex cord stromal tumors5.
The carcinoma diagnosis is aided by findings such as rare
psammoma bodies or a relationship with endometriosis in
the presence of a glandular structure. However, it must be
noted that epithelial markers such as cytokeratin and EMA
can be positive in malignant melanoma and negative in
carcinomas that have lost their antigenicity.
The presence of large epithelioid cells in malignant surface
epithelium tumors of the ovary can lead to confusion. The
oxyphilic variants of endometrioid clear cell carcinomas
and hepatoid carcinomas should be considered in the
differential diagnosis when large epithelioid cells have a
dark eosinophilic cytoplasm. Transitional cell carcinoma of
the ovary can contain small glands and small spaces and
can look similar to pseudopapillary-pattern malignant
melanomas with cystic degeneration. IHC helps to the
differential diagnosis in such cases5.
Ovarian sarcomas can also develop on a background of
dermoid cyst besides malignant melanoma. The presence
of epithelioid cells and melanin pigment helps in making the malignant melanoma diagnosis. Epithelioid or spindlecell
tumors that develop on a background of dermoid cyst
are evaluated as carcinosarcomas. Carcinosarcomas give
a positive reaction with epithelial markers and negative
reaction with melanocytic markers5.
Other tumors that are quite similar to ovarian melanomas
are sex cord stromal cell tumors and steroid cell tumors.
Both tumor cells have large eosinophilic cytoplasms.
Steroid cell tumors are not mitotically active like malignant
melanomas. They contain teratomatous elements. The
presence of spindle cells and melanin pigment supports the
diagnosis of malignant melanoma. Steroid cell tumors may
contain lipofucsin pigment. Malignant melanoma cases can
be confused with granulosa cell tumors when they consist
of cells with a narrow cytoplasm. The luteinized areas of
granulosa cell tumors may contain prominent nucleoli
but these are usually characterized by pale vesicular
nuclei. Granulosa cell tumors may also rarely be seen with
a dermoid cyst. Sex cord stromal tumors are positive for
inhibin and calretinin on IHC2. Steroid cell tumors
and sex cord stromal cell tumors are S-100 and melan-A
negative. HMB45 is the most specific melanocytic tumor
marker but one must not forget that it can also be positive in
steroid cell tumors of the ovary5. Dense melanin content
helped in the differential diagnosis from stromal tumors in
Other tumors to consider in the differential diagnosis are
lymphoma, leukemia, dysgerminoma, neuroectodermal
(NET) and primitive neuroectodermal tumors (PNET).
NET and PNET can be seen together with dermoid cyst and
dysgerminomas can develop from a teratoma. Lymphoid
and myeloid markers, PLAP, OCT-4, neuroendocrine
markers, CD99 and FLI-1 are important for the differential
diagnosis of these tumors in addition to melanocytic
The dense melanin pigment of the tumor indicated malignant
melanoma even at the intraoperative evaluation in our
case. The typical morphology and immunohistochemical
investigation provided the definite diagnosis.