Findings: PA radiograph shows a mediastinal mass (A, arrow) superimposed to the right hilum. In the lateral view the mass is faintly visible behind the distal trachea (B, circle). This location excludes a right hilar mass, because the right hilum is anterior to the trachea.

Enhanced coronal and sagittal CT confirm a posterior mediastinal mass (C-D, arrows) with necrotic areas and marked contrast enhancement. This is an important finding because it limits the differential diagnosis to four conditions: intrathoracic goiter, Castleman’s disease, paraganglioma and hemangioma.
Some of you have mentioned extramedullary hematopoiesis. In my (limited) experience I don’t recall seeing avid contrast enhancement in it. I have asked some friends and searched the web without finding a clear answer. If any of you have better information I am willing to be corrected. At any rate, this patient does not have any bone abnormalities, which makes the diagnosis of extrapulmonary hematopoiesis very unlikely.
 
Final diagnosis: posterior mediastinal paraganglioma surgically proved. A similar case was presented in case 168 of Caceres’ corner.
 
Congratulations to MK, who was the first to suggest the correct diagnosis.
 
Teaching point: remember the four mediastinal processes with avid contrast enhancement: intrathoracic goiter (frequent), Castleman´s disease and paraganglioma (uncommon) and hemangioma (never saw a case).

Findings: AP chest radiograph shows a well-defined opacity in the right upper hemithorax (A, arrow) which appears to be extrapulmonary. There are calcified granulomas in the left apex with retraction of the left hilum.

Unenhanced axial and coronal CT show an extrapulmonary mass with a calcified rim (B-C, arrows). The mass has a striated appearance, alternating lineal areas of different opacities. This CT appearance is practically pathognomonic of oleothorax (see case 19 of Caceres’ corner).

Instillation of oil in the extrapleural space (oleothorax, plombage) was used to collapse the lungs facilitating healing of TB cavities. It was abandoned in the early fifties after the discovery of effective antimicrobial therapy.
The patient had pulmonary TB in her youth and told us that it was treated by instillation of a substance. A clinical photograph in another patient (D) documents the surgical scar.

Final diagnosis: Oleothorax
 
Congratulations to Diogo, who was the first to make the diagnosis and to Jake, who concurred two days later.
 
Teaching point: this is an uncommon pathology, but it should be known because the appearance is pathognomonic and shouldn´t be confused with other conditions. This patient was seen four weeks ago and diagnosed initially of pleural tumour.

Findings: PA radiograph shows a faint opacity in the periphery of the left lower hemithorax (A, circle). A CT was recommended.

Axial CT shows an unexpected irregular basal opacity (B, arrow). Caudal slices show several parietal nodules (C-D, arrows).

Coronal CT shows the large basal opacity (D, arrow), as well as the small parietal nodules (D-E, red arrows).

The clue to the diagnosis lies in a negative finding: absent spleen in the left upper quadrant of the abdomen (D-E, asterisks), suggesting that the chest opacities may represent accessory spleens.
The patient was interrogated and stated a previous car accident with ruptured spleen and subsequent splenectomy. A test with labelled erythrocytes in another institution confirmed the accessory spleens.
 
Final diagnosis: thoracic splenosis
 
As I am writing this (12:00 PM Thursday), nobody has suggested the right diagnosis. I was expecting many correct answers, since I showed a similar case eight weeks ago (Diploma case 135).
 
Teaching point: remember the importance of negative findings (Diploma cases 135 and 136). In this particular patient, they were crucial to suggest the correct diagnosis.

Congratulations to MK, who made a last-minute diagnosis at 2:08 P.M. on Thursday!