Mediastinal mass and right lung, en block resection of mediastinal mass and right pneumonectomy specimen showing:
- Residual viable high-grade embryonal rhabdomyosarcoma with treatment effect.
- Tumor measures 13 cm in maximum dimension
- Approximately 40% of the tumor is viable.
- Bronchial resection margin is negative for tumor.
- Station 11 lymph nodes are negative tumor.
- Tumor extends right up to the inked pericardium but does not extend through it.
- The pulmonary vein margin is negative.
Final Diagnosis Comment:
The portion of the tumor which is viable shows a mixture of cell types. There is the high-grade spindle cell component which was seen on the initial biopsy. There are other areas which show transformation into bizarre pleomorphic tumor cells many of which have large amounts of eosinophilic cytoplasm and could be classified as anaplastic rhabdomyosarcoma which may be attributed to treatment effect. Some areas show more differentiated rhabdomyoblastic cells. Abnormal normal mitotic figures are readily identifiable.
Although the measurement of the tumor is given as 13 cm a lot of this measurement includes necrotic tumor. A measurement of residual viable tumor is very difficult as the zones of viable tumor are spread randomly throughout the entire lesion. Approximately 40% of the tumor is viable based on the gross appearance. There are pockets of viable tumor within the inferior portion of the upper lobe but they do not extend to the inferior diaphragmatic margin. There is extensive invasion into mediastinal fat and soft tissue. This portion of the tumor shows cystic change and is associated with large vascular channels.
The specimen is received in two containers; both labeled with the patient's name.
Container "A" is labeled as "query thymus". The specimen consists of an irregularly shaped piece of fibrofatty tissue measuring 4.0 cm x 1.8 x 5.0 mm. The specimen is sectioned and submitted in toto in cassettes "A1"-"A3".
The second part of the specimen is labeled "mediastinal mass and right lung". It consists of an en block resection specimen which, after fixation and inflation with formalin fixative, measures 22.0 cm x 20.0 cm x 6.0 cm. On the posterior and medial aspects of the specimen, there is attached pericardium, which measures 12.0 cm x 7.0 cm. Above this; a portion of the mediastinal mass is identified. This portion measures approximately 5.0 cm in maximum dimension. This is in continuity with the main part of the mass, which occupies most of the upper lobe. There are adhesions between the upper and lower lobes, but the tumor does not definitely extend into the lower lobe. The portion of attached pulmonary vein is painted with black ink and this resubmitted in toto in cassette "B1" from the frozen section. The diaphragmatic surface is painted with black ink and has a nodular consistency. The portion of diaphragm submitted for frozen section is resubmitted in cassette "B2". The portion of right mainstem bronchus measures 3.0 cm in length and has a diameter of 2.5 cm. There are marked adhesions around the hilar area. The pleural surfaces appear dusky and consistent with old hemorrhage. On sectioning the specimen, the tumor, which occupies most of the upper lobe, appear necrotic in that it is yellow and homogeneous in appearance. It is well circumscribed, and it measures 13.0 cm x 9.0 cm x 8.0 cm. Grossly, it comes right up to but not through the pericardium. The pericardial surface is inked blue. Tumor occupies the apical posterior and anterior segments of the upper lobe and the middle lobe. The apical portion is somewhat spared. Tumor does not appear to extend into the posterior segment. On cut section the mass appears homogeneous except for a few small white nodules measuring about 1 cm in maximum dimension, which may represent viable tumor.
Immunohistochemical staining confirms the given diagnosis. There is strong staining of the tumor cells with myoglobin and desmin. The myoglobin strongly stains the areas of the better differentiated cells and shows focal staining in the more spindled primitive areas. The pattern is similar for the desmin stain. The O13 stain shows stronger staining in the more primitive spindled areas and weak to no staining in the better differentiated areas.