Falsely low serum XXXX in two cases of invasive @entity2013 .

@entity808 @entity1 @entity227 @entity4089 @entity2013 @entity129 @entity5 @entity935 @entity189 @entity4090 @entity11 @entity4611 @entity1653 @entity4614 @entity3580 @entity977 @entity701
The differential diagnosis of @entity5 at the base of the skull comprises @entity1653 , @entity808 , @entity11 , @entity189 , @entity3580 , epidermoids, and @entity977 . About half of the @entity977 are @entity2013 which are unique in a sense that medical therapy causes rapid @entity5 shrinkage and symptomatic improvement. We report on two @entity1 in which the diagnosis of an invasive @entity2013 was masked by apparently low @entity4090 levels caused by a high-dose hook effect in the chemiluminometric assay. The first case a 49 year old male with impairment of hearing on the left side was presented in the Department of Otorhinolaryngology. A massive invasively growing @entity5 was demonstrated on a cranial MRI. Endocrine tests revealed @entity4611 . The @entity1 underwent debulking surgery, occipitocervical fusion because of destruction of the first cervical vertebra and subsequent irradiation. The histopathological diagnosis was invasive @entity2013 . A repeat @entity4090 (PRL) sample, which was assayed using serial dilutions, revealed a real PRL level of 89,700 ng/ml. @entity935 agonist therapy was initiated under which PRL levels declined in parallel with @entity5 size. The second case a 40 year old male was presented with acute @entity227 . Cranial MRI showed a large @entity5 at the base of the skull. Based on a transnasal biopsy, the preliminary diagnosis was a poorly differentiated @entity189 for which emergency irradiation was performed. Endocrine tests demonstrated partial @entity4614 and moderate @entity4089 . @entity701 was substituted and @entity935 agonist therapy was started because of moderate @entity4089 . The final histopathological diagnosis was invasive @entity2013 . A repeat PRL sample assayed in serial dilution demonstrated an apparent rise in PRL with a maximum value of 6,460 ng/ml. Under @entity935 agonist therapy, PRL declined to normal values, @entity5 size decreased and @entity129 disappeared. The apparently falsely low @entity4090 levels in the initial work-up of both @entity1 were caused by a high-dose hook effect in the PRL assay. Serial dilutions of serum PRL samples is, therefore, mandatory in the diagnostic work-up of @entity1 with large invasive @entity5 at the base of the skull. This avoids unnecessary aggressive and dangerous treatment like surgery or radiotherapy in cases where pharmacological treatment may be the choice.
