IMHO: Usually [if some vital parameters are met] IHC or genetic analysis on 'old pathology specimens'

(guessing you are talking about existing paraffin-blocks/possibility of producing paraffin sections to be stained or to be analyzed somehow or other....therefore it might be of benefit to define the ?material? the analysis/genetic study should be done)

is possible  (if there are suited AB's and / or  correlative [bio-]markers.

Admitting I never saw a pathological case of 'Carney Complex [abbrev,. CNC] ' only  as a quick shot: 

'Identification of a Novel Genetic Locus for Familial Cardiac Myxomas and Carney Complex'  by  Casey et al, in Circulation. 1998;98:2560-2566; doi: 10.1161/01.CIR.98.23.2560;             http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.620.1352&rep=rep1&type=pdf

Interesting Data (website's Last Update: January 29, 2015.):

@ https://www.ncbi.nlm.nih.gov/books/NBK1286/#carney.Molecular_Genetics, among other sections:    Nomenclature

Carney complex [NB: CNC] has also been designated by the following acronyms:

NAME (nevi, atrial myxomas, ephelides)

LAMB (lentigines, atrial myxoma, blue nevi)

There also, under section 'Differential Diagnosis': 

" Cardiac myxoma. Cardiac myxoma is the most common type of cardiac tumor in adults and accounts for approximately 30% of cardiac tumors in children. Genetic studies reveal no apparent association between CNC and sporadic myxomas [Fogt et al 2002].   Kindreds have been described with familial myxomas, CNC, and cardiomyopathy associated with a single pathogenic variant of a protein that belongs to the family of myosins [Veugelers et al 2004]. This condition is distinct from CNC and is either a separate disorder or the concurrence of two genetic disorders in one family [Stratakis et al 2004]. "

For those not sure about the 'disease': see  CARNEY 1995, The Carney complex (myxomas, spotty pigmentation, endocrine overactivity, and schwannomas).

(PMID:7712644)    

ABSTRACT: The Carney complex [NB: CNC]  is a multisystem tumorous disorder that features myxomas (heart, skin, and breast), spotty skin pigmentation (lentigines and blue nevi), endocrine tumors (adrenal, testicular, and pituitary), and peripheral nerve tumors (schwannomas). The condition is transmitted as an autosomal dominant trait. The most serious components of the syndrome are cardiac myxoma and psammomatous melanotic schwannoma. The cutaneous manifestations are a major clue to the disorder.  ....cf.:  http://europepmc.org/abstract/med/7712644

on: https://ghr.nlm.nih.gov/condition/carney-complex  or: 

https://ghr.nlm.nih.gov/condition/carney-complex#diagnosis    &  Info 

'Atrial myxoma': https://medlineplus.gov/ency/article/007273.htm

Naturally there are a lot of (scientific) sources and articles available via web-search. Best wishes & looking forward to see other, purposeful problem solutions....

 Thanks for your reply Sir.

Dear Dr. Jayanth Keshavamurthy, you're welcome. Hopefully there will be other answers too. Best regards, W.M.

Yes, it can be done. But it needs an experienced hand. Because 'trial and error method' in diagnosis of Carney complex  related to human  pathology is not so simple and easy task for a researcher and/ an untrained pathologist. It is unethical also to play with human life. First, be trained yourself under the supervision of a well experienced Oncopathologist and then opt for your formulated goal.

Carney complex an autosomal dominant hereditary  multisystem tumor disorder, basically characterized by unusual and abnormal pigmentation. A lot of published papers related to Carney complex disorder and mode of approaches for its diagnosis may be followed  for a successful diagnosis of heart.

Clinical and molecular features of the Carney complex: diagnostic ...

https://www.ncbi.nlm.nih.gov/pubmed/11549623

Carney Complex - NORD (National Organization for Rare Disorders)

https://rarediseases.org › ... › Rare Disease Information

Carney complex: an update - European Journal of Endocrinology

www.eje-online.org/content/173/4/M85.full

Cardiac Myxomas and the Carney Complex | Revista Española de ...

www.revespcardiol.org/en/cardiac-myxomas-and...carney/.../13128937/

 Kindly go through detailed protocol so as to meet your need.

 Thanks Abhimanyu.

Really,Carney complex a rare type autosomal dominant hereditary multisystem tumor disorder, mostly observed among the adolescents and youth in both sexes. On the basis of familial predisposition, stress should be given for finding out suitable molecular biomarkers so as to detect it at an early hand and to save the valuable life of the victimised individuals.