LWBK1006-35 LWW-Govindan-Review November 24, 2011 11:26
Chapter 35•Cancer of Unknown Primary Site 479ANSWERS
Answer 35.1. The answer is A.
In patients with cancer of unknown primary, the most common histol-
ogy seen on initial light microscopic exam is adenocarcinoma (60%).
Approximately 29% of these tumors are poorly differentiated carcinoma
or poorly differentiated adenocarcinoma, 5% are squamous carcinoma,
5% are poorly differentiated malignant neoplasm, and 1% are neuroen-
docrine carcinoma. Further identification usually requires specialized tests
including IHC staining, electron microscopy, and genetic analysis.Answer 35.2. The answer is D.
Aggressive neuroendocrine carcinomas of unknown primary site are usu-
ally found in multiple metastatic sites and rarely secrete bioactive pep-
tides. Histologic features and IHC staining can help guide further workup.
Bronchoscopy should be performed in patients with small-cell neuroen-
docrine carcinoma histology, or in patients with TTF-1 positive tumors.
Colonoscopy should be performed in patients with tumors staining posi-
tive for CDX2, to determine the primary site.Answer 35.3. The answer is A.
Common leukocyte antigen is specific for differentiating lymphoma from
carcinoma. TTF-1 is positive in 75% of cases of lung adenocarcinoma, as
well as small cell carcinoma. Cytokeratin 7 and 20 staining are increas-
ingly being used and can help guide further diagnostic workup, but are
not very specific. Chromogranin staining is suggestive of neuroendocrine
differentiation.Answer 35.4. The answer is B.
In a large clinical trial of 220 patients, some subsets were identified as
having a more favorable prognosis. These subsets include (i) tumors
in the retroperitoneum, mediastinum, or peripheral lymph nodes; (ii)
two or more features associated with germ cell syndrome; (iii) women
with peritoneal carcinomatosis; (iv) poorly differentiated neuroendocrine
tumors; (v) poorly differentiated neoplasm not otherwise specified; and
(vi) anaplastic lymphoma. Many of these patients were proven to have
thymomas, germ cell tumors, primary peritoneal carcinomatosis, lym-
phomas, and neuroendocrine carcinomas. These tumors are very respon-
sive to chemotherapy with a complete response rate in different clinical
trials ranging from 10% to 26%.Answer 35.5. The answer is B.
Extragonadal germ cell tumors usually occur in midline locations includ-
ing the mediastinum, retroperitoneum, or pineal region. This patient
presented with a pineal mass, normal testicular exam, and an elevated
serum hCG and AFP level, which are suggestive of an extragonadal germ