Diagnosis and Discussion - Case 1115

Final Diagnosis: METASTATIC, HIGH-GRADE SARCOMATOID YOLK SAC TUMOR (95%) WITH FOCI OF INTESTINAL-TYPE ADENOCARCINOMA (5%)

Discussion:

Given the high grade glandular morphology, immunohistochemical profile, and patient’s colonoscopy only up to the hepatic flexure, the lesion was initially favored to be a metastasis from a colorectal or appendiceal primary on the biopsy material until the FISH results demonstrating overexpression of chromosome 12p and isochromosome 12p (i12p)  were issued.

On follow up resection the mass was grossly ill-defined, tan-pink, soft to rubbery, with peripheral necrosis, and multiple cystic structures. Microscopically the specimen contained a few foci of intestinal-type adenocarcinoma (5%) in the background (95%) of a malignant pleomorphic spindled population. The glandular component redemonstrated a similar immunophenotype as the biopsy, while the spindled population was positive for Glypican-3, SALL4, and CAM 5.2. Given this immunohistochemical profile and the presence of i12p, the diagnosis of a sarcomatoid yolk sac tumor (YST) with a small focus of somatic malignancy was rendered.

Figure 4
Figure 4 – Malignant intestinal-type glandular component on the right adjacent to a malignant pleomorphic spindled population (10X).

It has been estimated that 2.5-8% of germ cell tumors (GCTs) harbor a somatic malignancy. These somatic type malignancies in GCT’s occur more commonly in metastatic sites than primary, such as in this case. Somatic malignancies originate either from teratomatous or YST components. The most common type of somatic malignancies are sarcomas, the majority of which are rhabdomyosarcoma. The second most common type of somatic malignancies are carcinomas, as we observed in this instance. An increase in tumor size after chemotherapy or “Growing teratoma syndrome” may clinically represent a somatic transformation. The clinical prognosis in patients with GCTs with associated somatic malignancy is significantly decreased if they are either the predominant component in gonadal GCTs or present in extragonadal locations. Complete surgical resection is the treatment of choice. Isochromosme 12p is considered specific for certain types of germ cell tumors (GCTs). It has been demonstrated to be present in 70% of all GCTs. It is also typically present in the somatic malignancy component, making it especially useful for diagnosis.

References:

  1. McKenney JK, Heerema-McKenney A, Rouse RV. Extragonadal germ cell tumors: a review with emphasis on pathologic features, clinical prognostic variables, and differential diagnostic considerations. Adv Anat Pathol. 2007; 14(2): 69-92.
  2. Freitag CE, Sukov WR, Bryce AH, et al. Assessment of isochromosome 12p and 12p abnormalities in germ cell tumors using fluorescence in situ hybridization, single-nucleotide polymorphism arrays, and next-generation sequencing/mate-pair sequencing. Hum Pathol. 2021; 112:20-34.
  3. El-Zaatari ZM, Ro JY. Mediastinal Germ Cell Tumors: A Review and Update on Pathologic, Clinical, and Molecular Features. Adv Anat Pathol. 2021; 28(5): 335-350.
  4. Guo CC, Czerniak B. Reprint of: somatic-type malignancies in testicular germ cell tumors. Hum Pathol. 2023; 133: 102-114.
  5. Sharmal S, Mishra K. Limitations in the diagnosis of childhood teratoid lesions on fine needle aspiration cytology. Acta Cytol. 2010; 54(2): 142-7.